Adhesive composition for use in an immunosensor

ABSTRACT

An adhesive composition for use in devices and methods for measuring a presence or a concentration of a particular component, such as an antigen, in a sample, such as blood, are provided. In one exemplary embodiment of an adhesive composition, the composition includes an adhesive, water, a poloxamer, and an anticoagulant. The adhesive can include particular properties, such as being hydrophilic, pressure-sensitive, heat-activated, and/or water soluble. The adhesive is particularly useful because it can help improve the flow of sample a device. For example, when the device is an immunosensor, the adhesive can help prevent the blood from clotting in chambers of the immunosensor. This results in a more efficient and accurate determination of the concentration of the sample. Methods of making the composition and device in which the composition can be used are provided, as are methods of using the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application based upon U.S. Ser. No.12/570,268, filed Sep. 30, 2009, the entire contents of which are hereinincorporated by reference.

FIELD

The present disclosure relates to adhesive compositions for use in bloodcontacting devices, such as an immunosensor, and methods for measuring aconcentration of a component associated with a sample, such as anantigen in a blood sample.

BACKGROUND

Analyte detection in physiological fluids, e.g. blood or blood derivedproducts, is of ever increasing importance to today's society. Analytedetection assays find use in a variety of applications, includingclinical laboratory testing, home testing, etc., where the results ofsuch testing play a prominent role in diagnosis and management in avariety of disease conditions. Analytes of interest include glucose fordiabetes management, cholesterol, and the like. In response to thisgrowing importance of analyte detection, a variety of analyte detectionprotocols and devices for both clinical and home use have beendeveloped.

One type of device used to detect and analyze blood samples areimmunosensors. Immunosensors generally include a plurality of electrodesand chambers that are configured to receive and analyze a sample. Thedifferent chambers of the immunosensor serve different purposes. Forexample, a fill chamber of an immunosensor can be configured to receivea sample, a reaction chamber can be configured to react the sample withan antibody disposed in the immunosensor, and a detection chamber can beconfigured to detect the presence or concentration of a protein orantigen within the sample following the reaction with the sample and theantibody. The various components of the immunosensor can be fabricatedby using, for example, a combination of substrates, plastics, laminates,and adhesives.

Conventional adhesives are used to bond materials like the substratesand the plastics together. This can be accomplished, for example, bycoating the adhesive on the substrate, laminating the adhesive, and thenbonding the laminated adhesive-substrate combination with the plasticlayer. Conventional adhesives are generally hydrophobic so that they canmaintain their bond in a wet environment. This, however, is a detrimentto the flow of liquid because liquid flow can be impeded by thehydrophobic properties of the adhesive. Thus, it can often be difficultfor blood samples to move between various chambers of an immunosensor.In particular, there can be a tendency for the sample to clot within theimmunosensor, thereby blocking movement of the sample through theimmunosensor. This can result in undesirable complications, errors, anddelays in analyzing the sample.

Accordingly, it would be desirable to improve the flow of blood throughan immunosensor, as well as improve the accuracy and speed ofmeasurements taken with an immunosensor.

SUMMARY

Devices and methods are generally provided for measuring a presence or aconcentration of a certain material within a sample. Adhesivecompositions for use in such devices and methods are also provided. Inone embodiment of an adhesive composition for use in an immunosensor,the composition includes an adhesive, water, a poloxamer, and ananticoagulant. The adhesive and the water can be combined to form amixture prior to being included with the poloxamer and theanticoagulant. The adhesive can have a number of different propertiesassociated with it, including being pressure-sensitive, heat-activated,and water soluble. In one embodiment the adhesive is a sulfopolyester.The anticoagulant can be selected from a group that includes heparin,citrate, ethylenediaminetetraacetic acid, and oxalate. The poloxamer caninclude units derived from ethylene oxide and propylene oxide. In oneembodiment the ethylene oxide and propylene oxide serve as monomers inblock copolymers. A concentration of the poloxamer with respect to theadhesive can be approximately in the range of about 0.05 to about 0.5percent. In an embodiment in which the anticoagulant is heparin, aconcentration of the heparin with respect to the adhesive can beapproximately in the range of about 0.1 to about 10 milligrams permilliliter.

One exemplary embodiment of an immunosensor can include a lowerelectrode, an upper electrode, and a separator disposed therebetween.The immunosensor can also include a plurality of chambers, including areaction chamber, a detection chamber, and a fill chamber. The reactionand detection chambers can each be formed in the separator, while thefill chamber can be formed at least partially in the separator and oneof the lower and upper electrodes. The fill chamber can be spaced adistance apart from the detection chamber, overlapping at least aportion of the reaction chamber. Further, a vent can be formed at leastpartially in each of the separator, the lower electrode, and the upperelectrode. The vent can be spaced a distance apart from the reactionchamber, overlapping at least a portion of the detection chamber. Ahydrophilic adhesive tape can be coupled to one of the lower and upperelectrodes and disposed over the vent, while a sealing component can becoupled to the other of the lower and upper electrodes and also disposedover the vent. The hydrophilic adhesive tape and the sealing componentcan be made from one or more of the same materials, including entirelyof the same material(s), or alternatively, can be made from one or moredifferent materials. The hydrophilic adhesive tape can form a wall ofthe fill chamber, and further, can have an anticoagulant incorporatedtherein.

The lower electrode can have a first reagent in liquid form and a secondreagent in liquid form disposed thereon. The first liquid reagent caninclude an antibody conjugated to an enzyme in a buffer, while thesecond liquid reagent can include ferricyanide, a substrate for theenzyme, and an electrochemical mediator in a dilute acid solution. Thefirst and second liquid reagents can be striped on the lower electrodeand dried. The upper electrode can have magnetic beads conjugated to anantigen striped and dried thereon. The immunosensor can be constructedsuch that the reaction chamber has the first reagent of the lowerelectrode and the magnetic beads conjugated to the antigen of the upperelectrode disposed therein and the detection chamber has the secondreagent of the lower electrode disposed therein.

The enzyme of the first liquid reagent of the lower electrode of theimmunosensor can be glucose dehydrogenase-PQQ and the buffer in whichthe enzyme can be located can include citraconate, sucrose, poloxamers,and calcium ions. The second liquid reagent of the lower electrode ofthe immunosensor can include ferricyanide, glucose, and phenazineethosulfate in a dilute citraconic acid solution. In one embodiment theanticoagulant of the adhesive tape can be heparin. A concentration ofthe heparin with respect to a concentration of the hydrophilic adhesivecan be approximately in the range of about 0.1 to about 10 milligramsper milliliter. The immunosensor can further include a meter disposedbelow the reaction chamber. In one exemplary embodiment the meter cancontain a magnet. The meter can be configured to apply a potentialbetween the lower and upper electrodes, as well as measure a resultingcurrent. In one embodiment a heating element can be associated with themeter. In another embodiment the meter can include a piercing componentthat is configured to pierce at least one of the hydrophilic tape andthe sealing component disposed over the vent.

One method for measuring a blood sample can include providing a reactionchamber and a detection chamber that are formed in a separator disposedbetween two electrodes. Further, a fill chamber that is at leastpartially formed in the separator and one of the two electrodes can alsobe provided. The fill chamber can be spaced a distance apart from thedetection chamber and can overlap at least a portion of the reactionchamber. Still further, a vent that is at least partially formed in theseparator and the two electrodes can be provided. The vent can be spaceda distance apart from the reaction chamber and can overlap at least aportion of the detection chamber. The method can further includeproviding an antibody-enzyme conjugate in a first buffer and magneticbeads linked to an antigen in a second buffer in the reaction chamber,and providing ferricyanide, glucose, and a mediator in a dilute acid inthe detection chamber. A first seal can be provided over a first side ofthe vent by way of a hydrophilic adhesive tape. The tape can also form awall of the fill chamber. A second seal can be provided over a secondside of the vent by way of a sealing component.

The method can further include providing a blood sample to the fillchamber such that at least a portion of the blood sample moves from thefill chamber to the reaction chamber. The vent can be opened after apre-determined time, for instance, by piercing at least one of thehydrophilic adhesive tape and the sealing component. Opening the ventafter a pre-determined time can allow portions of the blood samplecontaining the antibody-enzyme conjugate that is not bound to themagnetic beads to move to the detection chamber. Oxidation of theglucose in the detection chamber can be catalyzed, which can result inthe formation of ferrocyanide. The method can also include applying apotential between the two electrodes, electrochemically detecting acurrent from the ferrocyanide, and calculating a concentration of theantigen in the blood sample based on the signal detected.

In some embodiments of the method, the two electrodes can be heated. Inone embodiment the hydrophilic adhesive of the hydrophilic adhesive tapecan include heparin. A concentration of heparin with respect to aconcentration of the hydrophilic adhesive can be approximately 1milligram per milliliter. In another embodiment the hydrophilic adhesivecan include a poloxamer.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is an exploded view of one exemplary embodiment of animmunosensor in accordance with the present invention; and

FIG. 2 is a chart illustrating a measurement of C-reactive proteinsusing an immunosensor in accordance with the present invention.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The subject compositions, devices, and methods are suitable for use inthe determination of a wide variety of analytes in a wide variety ofsamples, and are particularly suited for use in the determination ofanalytes in whole blood, plasma, serum, interstitial fluid, orderivatives thereof. The compositions of the present invention caninclude any number of components in a variety of amounts andconcentrations. One having skill in the art will recognize thatcomponents, amounts, and concentrations discussed herein are merelyexamples for use in the present inventions and that a variety of othercombinations to form one or more compositions can be achieved in thespirit of the present disclosure.

Similarly, the compositions can be used in conjunction with a variety ofdifferent devices. Thus, to the extent compositions are discussed foruse with an immunosensor generally, the compositions can also be used inany number of devices, for instance, by way of non-limiting example,electrochemical cells, electrochemical sensors, hemoglobin sensors,antioxidant sensors, and biosensors. Non-limiting examples of some ofthe types of devices with which the adhesive compositions can be usedare discussed in greater detail in U.S. Pat. No. 5,942,102 of Hodges etal., entitled “Electrochemical Method” and filed on May 7, 1997, U.S.Pat. No. 6,174,420 of Hodges et al., entitled “Electrochemical Cell” andfiled on May 18, 1999, U.S. Pat. No. 6,379,513 of Chambers et al.,entitled “Sensor Connection Means” and filed on Sep. 20, 1999, U.S. Pat.No. 6,475,360 of Hodges et al., entitled “Heated Electrochemical Cell”and filed on Sep. 11, 2000, U.S. Pat. No. 6,632,349 of Hodges et al,entitled “Hemoglobin Sensor” and filed on Jul. 14, 2000, U.S. Pat. No.6,638,415 of Hodges et al., entitled “Antioxidant Sensor” and filed onJul. 14, 2000, U.S. Pat. No. 6,946,067 of Hodges et al., entitled“Method of Forming an Electrical Connection Between an ElectrochemicalCell and a Meter” and filed on Dec. 9, 2002, U.S. Pat. No. 7,043,821 ofHodges, entitled “Method of Preventing Short Sampling of a Capillary orWicking Fill Device” and filed on Apr. 3, 2003, and U.S. Pat. No.7,431,820 of Hodges et al., entitled “Electrochemical Cell” and filed onOct. 1, 2002, each of which is incorporated by reference in itsentirety.

Likewise, to the extent compositions are discussed for use with a devicehaving a particular configuration, any number of configurations can beused. For example, some configurations that can be used with the presentdisclosures include sensors having two electrodes facing each other,sensors having two electrodes on the same plane, and sensors havingthree electrodes, two of which are opposed and two of which are on thesame plane. These different configurations can occur in any number ofdevices, including the aforementioned devices.

Still further, the methods discussed herein, such as those related toforming compositions, constructing devices, and using devices, are alsonot limited by the particular steps or order of the steps. One havingskill in the art will recognize various orders in which the methods canbe performed, and further, will recognize that steps can be modified oradded without departing from the sprit of the invention.

In one exemplary embodiment of a composition for use in an immunosensor,the composition includes an adhesive, water, a poloxamer, and ananticoagulant. The adhesive can have a variety of properties associatedwith it in addition to being adhesive. These properties can result fromproperties associated with the particular adhesive that is used in thecomposition, or alternatively, they can result from the addition ofother components to the composition to assist in creating or enhancingthe properties. The adhesive can be hydrophilic for example, therebyallowing it to interact well with water and other liquids. In suchembodiments the adhesive can remain well-wet, which can result inallowing liquid samples to more easily flow through devices with whichthe composition is associated. One way of achieving an adhesive havinghydrophilic properties is by blending a hydrophilic, hemocompatiblepolymer into the adhesive. When devices that include an adhesive thatimproves flow are used in conjunction with blood samples, the use ofsuch adhesive can reduce the amount of clotting that occurs within thedevice. Improving flow can also speed up the time of various reactionsassociated with such devices. For example, in an immunosensor, acomposition that includes an adhesive that improves the flow of thesample can decrease the time it takes for an antigen-antibody reactionto occur. This is because a liquid sample that fills a biosensor slowlycan tend to dissolve the dried reagent and “push” it along the fillpath. In turn, regions of electrode that are depleted of the reagent canbe left behind, thus reducing the rate of the reaction.

The flow of fluid through devices associated with the composition canalso be improved by making the adhesive water soluble. Such a propertyalso helps the adhesive remain well-wet, and further, because it helpsimprove the flow, the other aforementioned benefits that result from animproved flow also result from a water soluble adhesive. Further, awater soluble adhesive can help prevent the release of volatile organiccompounds or toxic components when the adhesive is applied to a surfaceof devices such as immunosensors.

The adhesive can also be made pressure-sensitive and/or heat-activated.By making the adhesive pressure-sensitive and/or heat-activated, thedevice with which the adhesive is associated with can be more easilyprocessed. For example, the adhesive, and thereby the portion of thedevice with which the adhesive is associated, may not adhere strongly tocutting tools used to manufacture the device when the adhesive is madeto be heat-activated.

While a number of different adhesives can be used in conjunction withthe present composition, in one exemplary embodiment the adhesive is asulfopolyester. Other polyesters can also be used, such as polyestersand sulfopolyesters from the Eastman AQ™ polymer line.

Water associated with a composition can have its typical form and can beassociated with other components of the composition at any desired time.Filtered water, pure water, tap water, and treated water are allexamples of types of water that can be used in an adhesive composition.In an exemplary embodiment the water can be substantially free ofdissolved ions to allow an adhesive to more easily interact with thewater. This can occur because ions can help prevent the adhesive fromdissolving. In one exemplary embodiment the adhesive and the water aremixed together to form a mixture. When the adhesive includes propertiessuch as being hydrophilic and/or water soluble, the resulting mixturecan be easy to mix with other components of the adhesive composition,such as poloxamers and anticoagulants.

One or more poloxamers, which are sometimes referred to by their tradename Pluronics®, can be included as part of an adhesive composition toassist in making the composition hydrophilic. The one or more poloxamerscan be block co-polymers, e.g., nonionic tri-block copolymers, that canbe derived from and can include both polyoxypropylene, which issometimes referred to as poly(propylene oxide), and polyoxyethylene,which is sometimes referred to as poly(ethylene oxide). Propylene oxideand ethylene oxide can serve as monomers in the block copolymers.

The lengths of the blocks of the copolymers can be adjusted to create awide variety of different poloxamers, each having different propertiesbased on the particular composition of each of the poloxamers. Thepoloxamers can be blended into the adhesive directly or into thecomposition generally. Because many adhesives are hydrophobic, the useof poloxamers can enhance the performance of the adhesive composition.The ethylene oxide and propylene oxide polymer blocks can have a varietyof chemical structures to allow available poloxamers to exhibit variousranges of desirable and undesirable characteristics. For example, somepoloxamers work better to help fill an immunosensor with blood becausethey can help counteract the effects of high haematocrit blood. BASFPluronic® L 62 (also known as PE 6200) and BASF Pluronic® F 87 Prill arejust two examples of poloxamers that can assist in allowing animmunosensor to be filled with blood because of its ability to make thecomposition hydrophilic.

An adhesive composition can also include one or more anticoagulants. Theinclusion of anticoagulants can help reduce the risk of a liquid, suchas blood, from clotting in a device in which the composition is used.Further, anticoagulants can provide for more consistent fill behaviorwhen trying to fill a device with a liquid and/or when the liquid triesto move between various chambers in the device. The speed and extent ofa sample fill can be better controlled by including an anticoagulant inthe composition. The anticoagulant can be blended into an adhesivedirectly or it can be blended into the composition generally. Theanticoagulant can create surfaces that leach anticoagulant into a sampleas the sample fills the device. While many types of anticoagulants canbe used, some exemplary materials include heparin (including sodiumheparin and lithium heparin), citrate, ethylenediaminetetraacetic acid(sometimes referred to as EDTA), and oxalate.

The formation of an adhesive composition can be carried out in anynumber of ways. The methods discussed herein are merely examples of waysin which the various components can be combined to form one version ofthe adhesive composition. In view of the present disclosure, a personhaving ordinary skill in the art will recognize that the amounts of thecomponents included in the adhesive composition, which can include anadhesive(s), water, a poloxamer(s), and an anticoagulant(s), can bedelicately balanced in order to achieve a workable solution. Forexample, a composition that contains too much of an adhesive can preventa sample from properly filling an immunosensor. Further, a compositionthat contains too much of a poloxamer can cause the sample to not wantto de-wet, leading to the sample not flowing between the chambers of theimmunosensor. Likewise, a composition that contains too little of apoloxamer can cause the sample to not wet at all and can lead toundesired clotting of the sample within the chambers of theimmunosensor. Still further, a composition that contains too much of ananticoagulant can adversely affect the sample. For instance, when thesample is blood, too much of an anticoagulant can adversely affect thered blood cells of the sample. Accordingly, the particular balance ofthe components used to form the adhesive composition can be important toimproving the performance of the immunosensor.

In one exemplary embodiment of forming an adhesive composition, anadhesive and water are combined and mixed together to form a mixture ofthe same. For example, approximately 4.5 kg of Eastman AQ™ 2150, whichis a sulphonated poly(ethylene)terephthalate, can be combined withapproximately 13.5 L of pure water. The water can be substantially freeof dissolved ions so that dissolution of the adhesive is enhanced. TheEastman AQ™ 2150 can be substantially made from a water-dispersiblesulfopolyester having a small number of modifiers and additives. Afterforming the adhesive-water mixture, the mixture can be heated and thenstored. For example, the mixture can be placed in an oven heated toapproximately 140° F. for a period of about four days. It can be stirredfor a period of approximately five to ten minutes each day.Subsequently, the mixture can be stored at approximately 46° F. or less,which can help reduce microbial growth.

Either before mixing the adhesive with water or after the mixture isformed, one or more poloxamers can be mixed in. For example, BASFPluronic® L 62 can be mixed in a manner such that the finalconcentration of the poloxamer is approximately in the range of about0.05 to about 0.5 percent. In one exemplary embodiment the poloxamerrepresents approximately 0.1 percent of the composition. Similarly,either before mixing the adhesive with water or after the mixture isformed, one or more anticoagulants can be mixed in. In one exemplaryembodiment the anticoagulant(s) is mixed in after the poloxamer(s) ismixed in. Continuing the adhesive composition example from above,following the addition of the BASF Pluronic® L 62, sodium heparin can bemixed in a manner such that the final concentration of the heparincompared to the composition is approximately in the range of about 0.1.to about 10 mg/mL. In one exemplary embodiment the concentration of theheparin compared to the concentration of the composition isapproximately 1 mg/mL. One type of sodium heparin that can be used withthe present composition is Sigma Aldrich porcine mucosa heparin, whichcan have a concentration of approximately 172 units/mg. Together, thecombination of the adhesive (e.g., 4.5 kg of Eastman AQ™2150), the water(e.g., 13.5 L pure water), the poloxamer (e.g., BASF Pluronic® L 62 at aconcentration of approximately 0.1% with respect to the composition as awhole), and the anticoagulant (e.g., Sigma Aldrich porcine mucosaheparin at approximately 172 units/mg and combined to form aconcentration as a whole of approximately 1 mg/mL) can form an exemplaryadhesive composition.

The adhesive compositions that result from the present disclosures canbe used in a variety of different devices. The type of device with whichthey can be used can affect in what form the compositions will be used.In some embodiments the composition may be applied directly to a device,for example by painting it directly onto an electrode, while in otherembodiments it may first be painted onto a sheet before the sheet withthe composition disposed thereon is associated with the device withwhich it will be used. In one exemplary embodiment the adhesivecomposition can be coated on a sheet of biaxially-oriented polyethyleneterephthalate, which can sometimes be referred to as Mylar, to form anadhesive tape. The composition can be applied to such a sheet in avariety of ways, for example it can be applied using a K-bar. Othermethods for applying the composition to a sheet include, but are notlimited to, slot-head coating and curtain coating.

The adhesive compositions that result from the present disclosures arealso not limited to use with devices that measure various aspects ofblood. Rather, the adhesive compositions can be used in a variety ofmanners in which adhesives compositions can be useful. By way ofnon-limiting example, the adhesive compositions that result from thepresent disclosures can be used in treating wounds, for example, byincorporating the adhesive composition into a bandage. The components ofthe adhesive composition, which are discussed in greater detail below,can be balanced to create the desired effect for use on an adhesivebandage. The results of using the adhesive compositions on an adhesivebandage can include improved clotting by the adhesive bandage and areduction in tissue damage and/or pain when removing the adhesivebandage from a wound. Other uses of the adhesive composition in place ofstandard adhesives are also contemplated by the disclosures herein.

An immunosensor is one of the many types of devices with which theadhesive compositions of the present disclosure can be used.Immunosensors are generally configured to receive and analyze a sample,such as blood. While the adhesive compositions of the present disclosurecan be used with immunosensors having any number of configurations, inone exemplary embodiment the immunosensor can include lower and upperelectrodes with a separator disposed therebetween. The lower and upperelectrodes can be used interchangeably as the working and counter orcounter/reference electrodes. In fact, because voltage applied to theimmunosensor can be flipped and/or alternated, each of the lower andupper electrodes can serve as the working electrode and the counter orcounter/reference electrode at different stages. For ease of descriptionpurposes, in the present application the lower electrode will beconsidered the working electrode and the upper electrode the counter orcounter/reference electrode.

A plurality of chambers can be formed within the immunosensor inportions of at least one of the lower electrode, the upper electrode,and the separator. Examples of chambers that can be included are a fillchamber, by which a sample can be introduced into the immunosensor, areaction chamber, by which a sample can be reacted with one or moredesired materials, and a detection chamber, by which a concentration ofa particular component of the sample can be determined. The immunosensorcan also include a vent hole to allow air to enter and escape theimmunosensor as desired, an adhesive tape to selectively seal one sideof the vent hole, and an additional sealing component to selectivelyseal a second side of the vent hole. The adhesive tape can also form awall of the fill chamber.

As illustrated in FIG. 1, in one embodiment of an immunosensor 10, theimmunosensor 10 includes a lower electrode 12 having two liquid reagents30, 32 striped onto it. The lower electrode 12 can be formed using anynumber of techniques used to foam electrodes, but in one embodiment apolyethylene terephthalate (PET) sheet that is filled with bariumsulphate is sputter-coated with gold. Other non-limiting example offorming an electrode are disclosed in U.S. Pat. No. 6,521,110 of Hodgeset al., entitled “Electrochemical Cell” and filed on Nov. 10, 2000, thecontents of which is incorporated by reference in its entirety.Likewise, the liquid reagents 30, 32 can have a number of differentcompositions, but in one embodiment the first liquid reagent 30 includesan antibody conjugated to an enzyme, such as GDH-PQQ, in a buffer thatcontains sucrose, as well as Pluronics® (i.e., a poloxamer), citraconate(i.e., an anticoagulant), and calcium ions, while the second liquidreagent 32 includes a mixture of ferricyanide, glucose, and a secondmediator, such as phenazine ethosulfate, in an acidic buffer, such as adilute citraconic acid solution. The first and second liquid reagents30, 32 can be dried onto the lower electrode 12. A number of techniquescan be used to dry the reagents 30, 32, but in one embodiment, followingthe striping of the reagents 30, 32 on the lower electrode 12, one ormore infrared dryers can be applied to the reagents 30, 32. One or moreair dryers can also be used, for example, subsequent to the infrareddryers. References to a first reagent and a first liquid reagent and asecond reagent and a second liquid reagent herein are usedinterchangeably and are not necessarily an indication that the reagentsare in their liquid or dried form at a given time for a particularembodiment. Further, some of the components associated with the firstand second liquid reagents can be used interchangeably and/or in boththe first and second liquid reagents as desired. By way of non-limitingexample, an anticoagulant can be associated with either or both of thefirst liquid reagent 20 and the second liquid reagent 32.

A line can be formed in the sputter-coated gold between the reagents 30,32 such that an edge of one of the reagents 30, 32 is very close to, ortouches, the line. The line can be applied using laser ablation or witha sharp metal edge. In one exemplary embodiment the line can be appliedbefore the reagents 30, 32 are striped on the electrode. The line can bedesigned to electrically insulate the section of the lower electrode 12under the detection chamber from the section that will be under thereaction chamber. This can provide a better definition of an area of theworking electrode during the electrochemical assay.

The immunosensor 10 can also include an upper electrode 14 having one ormore magnetic beads 34 containing surface-bound antigens thereon. Theantigens can be configured to react with the antibody disposed on thelower electrode 12 and the sample within a reaction chamber 18, asdescribed in further detail below. One having skill in the art willrecognize that the components disposed on the lower electrode 12 and onthe upper electrode 14 can be interchangeable. Thus, the lower electrode12 can include one or more magnetic beads 34 and the upper electrode 14can include two liquid reagents 30, 32 striped onto it. Further,although in the illustrated embodiment the length of the electrode 12forms the length of the entire body of the immunosensor 10, in otherembodiments the electrode can be only a portion of a layer of animmunosensor that serves as the lower or upper electrode or multipleelectrodes can be disposed on a single layer of an immunosensor.

A separator 16 disposed between the lower and upper electrodes 12, 14can have a variety of shapes and sizes, but it generally is configuredto desirably engage the lower and upper electrodes 12, 14 to form theimmunosensor 10. In one exemplary embodiment the separator 16 isadhesive on both sides, although the adhesive associated with theseparator 16 can be separate from the adhesive composition used inconjunction with the immunosensor 10 as described in further detailbelow. The separator 16 can further include a release liner on each sideof the two sides of the separator 16. The separator 16 can be cut in amanner that forms at least two cavities. A first cavity can be formed toserve as a reaction chamber 18 and a second cavity can be formed toserve as a detection chamber 20. In one embodiment the separator 16 canbe kiss-cut such that the reaction chamber 18 is aligned with theelectrodes 12, 14 to allow an antigen-antibody reaction therein whilethe detection chamber 20 is aligned with the electrodes 12, 14 to allowfor the electrochemical determination of ferrocyanide therein.

In one embodiment the separator 16 can be placed on the lower electrode12 in a manner that allows the magnetic beads 34 of the upper electrode14 and the first reagent 30 of the lower electrode 12 to be at leastpartially disposed in the reaction chamber 18 and theferricyanide-glucose combination of the second reagent 32 of the lowerelectrode 12 to be at least partially disposed in the detection chamber20. It can be advantageous to include an anticoagulant in each of thefirst and second liquid reagents 30, 32 so that an anticoagulant isassociated with each of the reaction and detection chambers 18, 20. Insome embodiments, the combination of one of the upper and lowerelectrodes 12, 14 and the separator 16 can be laminated together to forma bi-laminate, while in other embodiments the combination of each of thelower electrode 12, the upper electrode 14, and the separator 16 can belaminated together to form a tri-laminate. It is within the spirit ofthe invention, however, to include additional layers as desired.

A fill chamber 22 can be formed by punching a hole into one of the lowerand upper electrodes 12, 14 and the separator 16. In the illustratedembodiment the fill chamber is formed by punching a hole in the lowerelectrode 12 and the separator 16 such that the hole in the lowerelectrode 12 overlaps the reaction chamber 18. As shown, the fillchamber 22 can be a distance apart from the detection chamber 20. Such aconfiguration allows a sample to enter the immunosensor 10 through thefill chamber 22 and flow into the reaction chamber 18 to be reacted, forexample with the first liquid reagent 30 that includes the antibodyconjugated to an enzyme in a buffer on the first electrode 12 and themagnetic beads 34 striped on the upper electrode 14, without enteringthe detection chamber 20. Once the sample has been reacted, it can thenflow into the detection chamber 20 for interaction with the secondliquid reagent 32, for example the mixture of ferricyanide, glucose, andthe second mediator in an acidic buffer.

A vent 24 can be formed by punching a hole through each of the twoelectrodes 12, 14 and the separator 16 such that the vent 24 extendsthrough the entirety of the immunosensor 10. The hole can be punched ina number of different locations, but in one exemplary embodiment it canoverlap a region of the detection chamber 20 that is spaced apart fromthe reaction chamber 18.

The vent 24 can be sealed in a number of different manners using anumber of different sealing components, but in the illustratedembodiment a first side of the vent 24 located on the lower electrode 12is sealed using a hydrophilic adhesive tape 40 that includes theadhesive composition of the present invention and a second side of thevent 24 located on the upper electrode 14 is sealed using a sealingcomponent, such as Scotch® tape 42. The adhesive tape 40 can be formedin a variety of manners, including by being coated on a sheet ofbiaxially-oriented polyethylene terephthalate, as discussed above. Theadhesive sides of both the adhesive tape 40 and the Scotch® tape 42 canboth face the immunosensor 10. As shown, not only can the adhesive tape40 form a seal for the vent 24, but it can also form a wall for the fillchamber 22 so that the sample can be contained therein. In embodimentsin which the adhesive tape 40 includes the adhesive composition of thepresent disclosure, the properties of the adhesive tape 40 can thus beassociated with the fill chamber 22. Accordingly, a surface of the fillchamber 22 can be hydrophilic and/or water soluble, thereby allowing itto remain well-wet when the sample is disposed therein. Both theadhesive tape 40 and the Scotch® tape can be selectively associated anddisassociated with the immunosensor 10 to provide venting and/or sealingfor the immunosensor 10 and the components disposed therein as desired.One having skill in the art will recognize that Scotch® tape 42 is justone example of a sealing component, and that many other types ofcomponents capable of sealing the vent 24 can also be used, includingthe hydrophilic adhesive tape 40.

The advantage of using an anticoagulant, such as heparin, as part of theadhesive composition are illustrated by the chart of FIG. 2. Theinclusion of heparin in one embodiment of an adhesive compositionimproved the ability of the immunosensor to more easily function withblood over a wide range of clinically relevant hematocrits. As shown, ameasurement of C-reactive proteins for both a hematocrit of 33.5% and47.5% show that the concentration of the reference plasma and theactually sensed concentration are relatively consistent over a data set.Perfectly ideal results would form a straight line with theconcentration of C-reactive protein measured by the meter equaling thereference concentration of C-reactive protein for each data point. Theactual data results are either near such a theoretical line, or to theextent they are spaced from such a line, the data points are generallyequidistant from both sides of the line, indicating that with largesample sizes the results would also likely approach the theoreticalline. Thus, the present invention results in immunosensors that aregenerally accurate.

While the present disclosure discusses a variety of differentembodiments related to immunosensors in which the adhesive compositionsdiscussed herein can be used, other embodiments of immunosensors canalso be used with the adhesive compositions of the present disclosure.Non-limiting examples of such embodiments include those described inU.S. Patent Application Publication No. 2003/0180814 of Hodges et al.,entitled “Direct Immunosensor Assay” and filed on Mar. 21, 2002, U.S.Patent Application Publication No. 2004/0203137 of Hodges et al.,entitled “Immunosensor” and filed on Apr. 22, 2004, U.S. PatentApplication Publication No. 2006/0134713 of Rylatt et al., entitled“Biosensor Apparatus and Methods of Use” and filed on Nov. 21, 2005, andU.S. patent application Ser. No. 12/563,091, which claims priority toeach of U.S. Patent Application Publication Nos. 2003/0180814 and2004/0203137, each of which is incorporated by reference in itsentirety.

In one embodiment the immunosensor 10 can be configured to be placedinto a meter that is configured to apply a potential to the electrodes12, 14 and measure a current that results from the application of thepotential. The meter can include a number of different features. Forexample, the meter can include a magnet that is configured to maintaincertain components of the immunosensor 10 in one chamber while othercomponents flow to the other. In one exemplary embodiment the magnet ofthe meter is located such that, upon placing the immunosensor 10 in themeter, the magnet is disposed below the reaction chamber 18. This canallow the magnet to assist in holding back any magnetic beads 34, andmore particularly any antibody-enzyme conjugate that is bound to thebeads 34, from flowing into the detection chamber 20. Another optionalfeature of the meter is a heating element. A heating element can helpspeed up the reaction rate and help the sample flow through theimmunosensor 10 in a desired manner by reducing the viscosity. Asdescribed in greater detail below, a piercing instrument can also beassociated with the meter.

In use, the immunosensor 10 can determine a concentration of an antigenof a sample. The immunosensor 10 can be connected to a meter. The samplecontaining the antigen to be determined can be loaded into theimmunosensor 10 by placing it into the fill chamber 22 of theimmunosensor 10. The sample can be placed using a variety of techniques,but in one exemplary embodiment a drop of blood from a fingertip can bedrawn by capillary action into the fill chamber 22. The sample can flowfrom the fill chamber 22 and into the reaction chamber 18 because of theconfiguration of the immunosensor 10. Inside the reaction chamber 18 canbe the first reagent 30, which can include an antibody conjugated to anenzyme in a buffer containing sucrose, poloxamers, and calcium ions, andmagnetic beads 34, which can contain surface-bound antigens. Both thefirst reagent 30 and the magnetic beads 34 can be configured to play arole in the reaction of the sample. The antigen of the magnetic beads 34and of the sample can block binding sites of the antibody of the firstreagent 30 in a manner that prevents the conjugate of the first reagent30 from binding to the antigen on the surface of the magnetic beads 34.After a predetermined amount of time elapses, for example two to fiveminutes, the adhesive tape 40 that is disposed over the vent 24 of thelower electrode 12 can be pierced. In one exemplary embodiment the meterwith which the immunosensor 10 is associated with includes a piercinginstrument for piercing the vent 24. Examples of a piercing instrumentinclude a needle or other sharp tool.

The time that elapses after a sample is added to the sensor 10 butbefore the vent 24 is pierced can vary depending on the particularapplication with which the sensor 10 is used and the particularcomponents that form the sensor 10. After a sample is introduced intothe reaction chamber 18, it takes time to dissolve the reagents 30, 32.A variety of factors can affect the time it takes to dissolve thereagents 30, 32, which include, by way of non-limiting examples, thechemical make-up, viscosity, and amount of the sample with which thesensor 10 is being used, as well as the temperature of the environmentwithin and surrounding the sensor 10. For example, blood having a highhaematocrit can take longer to dissolve the reagents 30, 32 than bloodhaving a lower red blood cell content. Likewise, it can take longer todissolve the reagents 30, 32 at cooler temperatures.

The time it takes for the conjugate to bind to the magnetic beads 34 canalso be factor that varies depending on the particular application withwhich the sensor 10 is used and the particular components that form thesensor 10. By way of non-limiting examples, the time it takes for theconjugate to bind to the beads 34 can depend on the viscosity of thesample, the affinity between the analyte and the antibody portion of theconjugate, and the temperature of the incubation. Typically at leastsome of the binding between the conjugate and the beads 34 can occurbefore all of the reagents 30, 32 have been dissolved.

In one exemplary embodiment, a minimum time allowed to elapse before thevent 24 is pierced can be approximately two minutes when the reaction isbeen carried out at approximately 37° C. In another exemplaryembodiment, a minimum time allowed to elapse before the vent 24 ispierced can be approximately five minutes when the reaction is carriedout at approximately 20° C. If not enough time is permitted to elapse,accuracy can be affected by there being an inadequate reaction betweenthe antigen and the antibody. In contrast, if too much time is permittedto elapse, accuracy can be affected due to the possible evaporation ofthe samples as a result of the small volumes with which the sensor 10 isused. Additionally, allowing too much time to elapse is generally notpreferred from a practicality standpoint—it is generally preferred toconduct the reaction as quickly as possible.

A magnet of the meter can assist in holding back the magnetic beads 34and any antibody-enzyme conjugate that is bound to the beads fromleaving the reaction chamber 18, either by exiting through the vent 24or flowing into the detection chamber 20. The remaining portions of theconjugate can enter the detection chamber 20. In the detection chamber20 can be the second reagent 32 on the lower electrode 12, which caninclude the mixture of ferricyanide, glucose, and a second mediator inan acidic buffer. The conjugate that flows from the reaction chamber 18to the detection chamber 20 can catalyze oxidation of glucose of thesecond reagent 32. The oxidation of glucose can result in the formationof ferrocyanide. The presence and amount of ferrocyanide can be detectedelectrochemically within the detection chamber 20, which in turn can beused to calculate the concentration of the antigen in the sample. Theresult can be transmitted to a display mechanism in any number of ways.

One having skill in the art will recognize that although variouscomponents of the immunosensor 10 are discussed making reference to aspecific material, a variety of other materials that can achieve similarresults can also be used. By way of non-limiting example, although it isdescribed that a PET sheet is sputter-coated with gold, in otherembodiments a PET sheet can be sputter-coated with other metals such aspalladium, platinum, iridium, silver, and mixtures thereof, or othermaterials that have properties that achieve similar results. Further,one skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. An adhesive composition for use in an immunosensor, comprising: anadhesive; water; a poloxamer; and an anticoagulant.
 2. The adhesivecomposition of claim 1, wherein the anticoagulant is selected from thegroup consisting of: heparin, citrate, ethylenediaminetetraacetic acid,and oxalate.
 3. The adhesive composition of claim 1, wherein thepoloxamer comprises units derived from ethylene oxide and propyleneoxide.
 4. The adhesive composition of claim 3, wherein ethylene oxideand propylene oxide serve as the monomers in block copolymers.
 5. Theadhesive composition of claim 1, wherein the adhesive ispressure-sensitive.
 6. The adhesive composition of claim 1, wherein theadhesive is heat-activated.
 7. The adhesive composition of claim 1,wherein the adhesive is water soluble.
 8. The adhesive composition ofclaim 1, wherein the adhesive is a sulfopolyester.
 9. The adhesivecomposition of claim 1, wherein a concentration of the poloxamer withrespect to the adhesive is approximately in the range of about 0.05 toabout 0.5 percent.
 10. The adhesive composition of claim 2, wherein aconcentration of the heparin with respect to the adhesive isapproximately in the range of about 0.1 to about 10 milligrams permilliliter.
 11. The adhesive composition of claim 1, wherein theadhesive and the water are combined to form a mixture prior to beingincluded with the poloxamer and the anticoagulant.